This is really testing two classes of compounds, ionic compounds and acids. For ionic compounds, the naming convention is cation + anion, in that order. The cation is generally just the name of the element, but the anion can be more complex. If it is monatomic, it should end in -ide (eg bromide rather than bromine, nitride rather than nitrogen, oxide rather than oxygen). For polyatomic ions, it is useful to memorize the important ones, and then look for patterns. You will never have an anion that is named the same as the element (eg sodium chlorine).
For acids with monatomic "anions", the naming convention is hydro___ acid. HBr is hydrobromic, and HF is hydrofluoric, for example. Some very weak acids are named as ionic compounds rather than acids; H2S is named hydrogen sulfide rather than hydrosulfuric acid. For acids with polyatomic "anions" Fluorine's rules are very helpful.
Don't worry about prefixes in front of cations. When we are talking about ionic compounds, they do not matter. Na2O is not disodium oxide, but just sodium oxide. Also, remember that the overall molecule has to be neutral, meaning the positive cations and the negative anions have to cancel out. For some polyatomic anions, the charge has to be memorized. With a lot of practice and increased chemical intuition, you will learn to deduce this. I would really go back and read your book and notes more. Some of the mistakes you've made are indicative of lack of understanding of the chemistry behind ionic compounds and acids. Rules for nomenclature are important, but so is understanding the chemistry. An example would be HF4, which is clearly not possible because hydrogen cannot bond to 4 things.